Plate end portion detecting device and plate end portion detecting method

Abstract

This plate end portion detecting device comprises: a plurality of ferromagnetic core materials which are installed side by side in the width direction of the plate end portion detecting device, each of the plurality of ferromagnetic core materials being provided with an excitation coil; a plurality of detecting coils which correspond respectively to the plurality of ferromagnetic core materials and which detect a signal corresponding to the strength of a magnetic field obtained by reflecting influence of a steel plate on the magnetic field generated in the excitation coil of the corresponding ferromagnetic core material when an AC voltage is applied to the excitation coil; a voltage control unit which controls the voltages applied to the excitation coils of the plurality of ferromagnetic core materials; and an arithmetic processing unit which detects the position of a plate end portion of the steel plate from a relationship between the amount of change in the signal detected by the detecting coil and the position of the detecting coil when the AC voltage is applied to the excitation coil. When the AC voltage is applied to the excitation coil, the voltage control unit performs control to apply a voltage to the excitation coil of at least one ferromagnetic core material among the ferromagnetic core materials present in a range in which magnetic flux leaks from the ferromagnetic core material provided with the excitation coil to which the AC voltage is applied, among the plurality of ferromagnetic core materials.

Description

Plate edge detection device and plate edge detection method

[0001] The present disclosure relates to a plate edge detection device and a plate edge detection method.

[0002] For example, a cooling device for cooling a steel sheet has a plurality of conveying rolls installed therein, and the steel sheet is conveyed through the cooling device while being placed on the plurality of conveying rolls. When the steel sheet is conveyed, the steel sheet may meander due to thermal expansion of the conveying rolls or a defect in the flat shape of the steel sheet. In order to suppress the meandering of the steel sheet, for example, conveying roll position control is performed to change the positions of the conveying rolls. In order to perform conveying roll position control, it is necessary to accurately detect the positions of the ends of the steel sheet in the sheet width direction (hereinafter referred to as "sheet ends").

[0003] Here, the following techniques have been proposed as techniques for detecting the positions of the plate ends of a steel plate: For example, Japanese Patent Laid-Open No. 2009-250898 (Patent Document 1) discloses a technique in which the surface of a coil around which a steel plate is wound is irradiated with light, an image of the coil surface is captured, and the positions of the plate ends of the coil are detected based on the brightness of the captured image.

[0004] Furthermore, Japanese Patent Laid-Open Publication No. 55-147373 (Patent Document 2) discloses a technology that uses a sensor having a ferrite with three protrusions on the top and bottom, a reference coil wound around the protrusion in the center of the upper side of the ferrite, and a detection coil wound around the protrusion in the center of the lower side of the ferrite, and detects the position of the plate end of a steel plate based on the change in inductance of the detection coil when a magnetic field is generated in the reference coil.

[0005] However, since the inside of a cooling device that cools a steel plate is an environment in which visible light and infrared light are blocked by water vapor, a large amount of water, etc., it is difficult to obtain an image containing enough brightness to detect the position of the plate edge of the steel plate in such an environment. Therefore, it is difficult to detect the position of the plate edge of a steel plate being transported inside the cooling device using the technology described in Patent Document 1.

[0006] In contrast, magnetic fields are not affected by water vapor or large amounts of water, so when detecting the position of the plate end of a steel plate based on the change in inductance of a detection coil when a magnetic field is generated in a reference coil, as in the technology described in Patent Document 2, it is possible to avoid being affected by water vapor or large amounts of water.

[0007] However, in the technology described in Patent Document 2, since a single sensor is used to detect the position of the end of the steel sheet, it is difficult to detect the position of the end of the steel sheet when the position of the end of the steel sheet fluctuates significantly in the width direction due to meandering of the steel sheet. Also, the steel sheet may travel while floating from its normal traveling position (called the pass line). In such cases, it is impossible to distinguish whether a change in the signal generated in the sensor is due to a change in the position of the end of the steel sheet or due to the floating. Therefore, the performance of detecting the position of the end of the steel sheet is reduced when the steel sheet floats.

[0008] Therefore, the present disclosure aims to provide a plate edge detection device and a plate edge detection method that can detect the position of the plate edge of a steel plate even when the position of the plate edge of the steel plate fluctuates significantly in the plate width direction in an environment where visible light and infrared light are blocked by water vapor or a large amount of water, such as inside a cooling device that cools steel plate.

[0009] A first aspect of the present disclosure is a plate edge detection device that detects the position of the plate edge of a steel plate conveyed in a cooling device that cools the steel plate, the plate edge detection device including a plurality of ferromagnetic core materials that are arranged side by side in a width direction of the plate edge detection device corresponding to the plate width direction of the steel plate and each provided with an excitation coil, a plurality of detection coils that correspond to each of the plurality of ferromagnetic core materials and detect a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on a magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil of the corresponding ferromagnetic core material, and a plurality of detection coils that detect a signal corresponding to the strength of a magnetic field applied to the excitation coil of the plurality of ferromagnetic core materials. and a calculation processing unit that detects the position of the plate end of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil, wherein the voltage control unit controls the application of voltage to the excitation coil of at least one ferromagnetic core material among the plurality of ferromagnetic core materials that is present within a range where magnetic flux leaks from the ferromagnetic core material to which the excitation coil to which the AC voltage is applied is provided, when an AC voltage is applied to the excitation coil.

[0010] A second aspect of the present disclosure is a plate edge detection device that detects the position of the plate edge of a steel plate being transported through a cooling device that cools the steel plate, the plate edge detection device comprising: a ferromagnetic core material provided with an excitation coil; a plurality of detection coils that are arranged side by side in the width direction of the plate edge detection device, which corresponds to the plate width direction of the steel plate, and that detect a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on the magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil; a voltage control unit that controls the application of voltage to the excitation coil; and an arithmetic processing unit that detects the position of the plate edge of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil, wherein the ferromagnetic core material and the excitation coil are arranged to extend in the width direction, and the voltage control unit controls the application of AC voltage to the excitation coil of the ferromagnetic core material that is arranged to extend in the width direction.

[0011] A third aspect of the present disclosure is a plate edge detection method for detecting the position of the plate edge of a steel plate conveyed in a cooling device that cools the steel plate, the method including: a plurality of ferromagnetic core materials arranged side by side in a width direction of the plate edge detection device corresponding to the plate width direction of the steel plate, each provided with an excitation coil; a plurality of detection coils corresponding to each of the plurality of ferromagnetic core materials, each detecting a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on a magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil of the corresponding ferromagnetic core material; a voltage control unit controlling the voltages applied to the excitation coils of the plurality of ferromagnetic core materials; and an arithmetic processing unit detecting the position of the plate edge of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil, and The plate end detection method includes: a voltage control step of controlling the voltage applied to the excitation coil of a magnetic core material; a detection step of using the plurality of detection coils to detect a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on the magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil of the corresponding ferromagnetic core material; and a calculation processing step of using the calculation processing unit to detect the position of the plate end of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil, wherein the voltage control step controls the application of a voltage to the excitation coil of at least one ferromagnetic core material among the plurality of ferromagnetic core materials that is present within a range where magnetic flux leaks from the ferromagnetic core material to which the excitation coil to which the AC voltage is applied is provided when the AC voltage is applied to the excitation coil.

[0012] A fourth aspect of the present disclosure is a plate edge detection method for detecting the position of an edge of a steel plate conveyed in a cooling device that cools the steel plate, the method comprising: a ferromagnetic core material provided to extend in a width direction of the plate edge detection device corresponding to the plate width direction of the steel plate and provided with an excitation coil; a plurality of detection coils arranged side by side in the width direction and detecting a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on a magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil; a voltage control unit that controls application of voltage to the excitation coil; and a method for detecting the position of the plate edge of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil. a voltage control step of using the voltage control unit to control the application of AC voltage to the excitation coils of ferromagnetic core materials extending in the width direction, a detection step of using the plurality of detection coils to detect signals corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel sheet on the magnetic field generated in the excitation coils when an AC voltage is applied to the excitation coils of the corresponding ferromagnetic core materials, and a calculation processing step of using the calculation processing unit to detect the position of the plate end of the steel plate from the relationship between the amount of change in the signal detected by the detection coils and the position of the detection coils when an AC voltage is applied to the excitation coils.

[0013] According to the present disclosure, a plate edge detection device and a plate edge detection method are provided that can detect the position of the plate edge of a steel plate even when the position of the plate edge of the steel plate fluctuates significantly in the plate width direction in an environment where visible light and infrared light are blocked by water vapor or a large amount of water, such as inside a cooling device that cools steel plate.

[0014] 1 is a plan view showing an example of the overall configuration of a plate edge detection device according to a first embodiment of the present disclosure and a steel plate transported by a plurality of transport rolls. FIG. 2 is a side view showing an example of the overall configuration of a plate edge detection device according to the first embodiment and a steel plate. FIG. 3 is a perspective view showing an example of a plurality of sensors according to the first embodiment. FIG. 4 is a front view showing an example of the configuration of a sensor according to the first embodiment. FIG. 5 is a diagram showing an example of a method for applying voltages to a plurality of excitation coils according to the first embodiment. FIG. 6 is a diagram showing an example of a flow of magnetic flux when voltages are applied to a plurality of excitation coils by the voltage application method according to the first embodiment. FIG. 7 is a block diagram showing an example of the configuration of a processing device according to the first embodiment. FIG. 8 is a flowchart showing an example of the flow of plate edge detection processing according to the first embodiment. FIG. 9 is a diagram showing an example of a method for applying voltages to a plurality of excitation coils according to a second embodiment. FIG. 10 is a diagram showing an example of a method for applying voltages to a plurality of excitation coils according to a third embodiment. FIG. 11 is a perspective view showing an example of a sensor according to a fourth embodiment. FIG. 12 is a front view showing an example of a sensor according to the fourth embodiment. FIG. 13 is a block diagram showing an example of the configuration of a processing device according to the fourth embodiment. FIG. 14 is a flowchart showing an example of the flow of plate edge detection processing according to the fourth embodiment. FIG. 15 is a diagram showing an example of a method for applying voltages to a plurality of excitation coils according to a reference example. FIG. 16 is a diagram showing an example of a flow of magnetic flux when voltages are applied to a plurality of excitation coils by the voltage application method according to the reference example.

[0015] First Embodiment First, a first embodiment of the present disclosure will be described.

[0016] 1 and 2 show an example of the overall configuration of a strip edge detection device 10 according to a first embodiment of the present disclosure and a steel sheet 14 transported by a plurality of transport rolls 12. For example, a cooling device 16 that cools the steel sheet 14 has a plurality of horizontally arranged transport rolls 12 installed therein. The transport rolls 12 are arranged parallel to one another. The steel sheet 14 is transported through the cooling device 16 while being placed on the transport rolls 12. The X-axis direction indicates the width direction of the steel sheet 14, and the Y-axis direction indicates the transport direction of the steel sheet 14. Hereinafter, the transport direction of the steel sheet 14 will be referred to as the "transport direction," and the width direction of the steel sheet 14 will be referred to as the "strip width direction." The width direction of the strip edge detection device 10 will be referred to as the "device width direction." The device width direction corresponds to the strip width direction. The device width direction refers to the direction perpendicular to the transport direction when viewed from the normal direction of the surface of the steel sheet 14.

[0017] The plate edge detection device 10 is a device that detects the plate edge (i.e., plate edge 14A) of a steel plate 14 being transported within a cooling device 16, and has a plurality of sensors 18 and a processing device 20.

[0018] The multiple sensors 18 are arranged side by side in the width direction of the device in the space between two adjacent transport rolls 12 and the path through which the steel sheet 14 passes. The configuration of each sensor 18 will be described in detail later. Each sensor 18 (see FIGS. 3 and 4 ) is a non-contact magnetic sensor having a yoke 24, an excitation coil 26, and a detection coil 28. The sensor 18 is installed on a stand 22 so that the magnetic flux emitted from the yoke 24 reaches the steel sheet 14 when the steel sheet 14 is directly above the sensor 18. However, the sensor 18 is positioned a certain distance away from the steel sheet 14 to provide heat resistance and impact resistance. The multiple sensors 18 include a sensor 18 located outside the steel sheet 14, even when a steel sheet 14 of the maximum width that can be transported through the cooling device 16 is transported. Here, the yoke is an example of a ferromagnetic core material of the present disclosure.

[0019] The processing device 20 is electrically connected to each of the multiple sensors 18, applies a voltage to the excitation coil 26, and detects the position of the plate end of the steel plate 14 based on a signal detected by the detection coil 28 in accordance with the strength of the magnetic field obtained by reflecting the influence of the steel plate 14 on the magnetic field generated in the excitation coil 26.

[0020] Fig. 3 shows an example of a plurality of sensors 18 arranged in the device width direction, and Fig. 4 shows an example of the configuration of each sensor 18. The plurality of sensors 18 have the same configuration. Each sensor 18 has a yoke 24, an excitation coil 26, a detection coil 28, and a pair of bobbins 30. The yoke 24 is made of a magnetic material such as a ferrite core, and has a pair of core portions 32 and a connecting portion 34. The pair of core portions 32 extend vertically, and the connecting portion 34 connects the lower ends of the pair of core portions 32 to each other.

[0021] Each bobbin 30 is formed in a cylindrical shape. A core portion 32 is inserted into the inside of each bobbin 30, thereby attaching each bobbin 30 to the core portion 32. The excitation coil 26 is wound around one of the pair of core portions 32 via the bobbin 30, and the detection coil 28 is wound around the other of the pair of core portions 32 via the bobbin 30.

[0022] The yoke 24 is a component that functions as a ferromagnetic core material for the excitation coil 26 and the detection coil 28. By providing the yoke, it is possible to detect magnetic characteristics with high sensitivity. Each yoke 24 is installed so that the pair of core portions 32 are aligned in the conveyance direction. Furthermore, multiple yokes 24 are arranged side by side in the device width direction. The detection coil 28 provided in each yoke 24 corresponds to the excitation coil 26 provided in the same sensor 18.

[0023] The sensor 18 may be configured such that the excitation coil 26 and the detection coil 28 are separate coils that are wound independently around each core portion 32, or a single coil may be wound continuously around each core portion 32 as the excitation coil 26 and the detection coil 28. The following description will continue using, as an example, a configuration in which the sensor 18 is configured such that a single coil is wound continuously around each core portion 32 as the excitation coil 26 and the detection coil 28.

[0024] When the steel sheet 14 is not present above the sensor 18, the magnetic flux emitted from the yoke 24 on which the excitation coil 26 is mounted is absorbed by the south pole of the yoke 24 on which the detection coil 28 of the same sensor 18 is mounted. On the other hand, when the steel sheet 14 is present above the sensor 18, eddy currents are generated due to the time-dependent change in the magnetic flux. The eddy currents generate a magnetic field that cancels out the magnetic flux emitted from the yoke 24 on which the excitation coil 26 is mounted. The strength of the magnetic field detected by the detection coil 28 changes as the spatial distribution of the magnetic flux is canceled out by the eddy currents generated by the presence of the conductive steel sheet 14. By utilizing this phenomenon, a signal detected by the detection coil 28 corresponding to the magnetic field strength obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated by the excitation coil 26 is acquired for each position of the sensor 18. The position of the edge of the steel sheet 14 can be detected based on the relationship between the change in the acquired signal and the position of the sensor 18. The signal corresponding to the magnetic field strength can be expressed in terms of electromagnetic characteristics such as impedance (inductance), voltage, and current.

[0025] Here, the inventor noticed that there was a problem when detecting the position of the edge of the steel plate 14 using the plate edge detection device 10. Below, we will explain the problem that the inventor thought about with respect to the plate edge detection device 10. When detecting the position of the edge of the steel plate 14 using the plate edge detection device 10, the inventor first thought of applying voltages to the multiple excitation coils 26 as follows.

[0026] Fig. 15 shows an example of a method for applying voltage to a plurality of excitation coils 26 according to a reference example. The upper diagram in Fig. 15 shows the relationship between the positions of the sensors 18 to which voltages are applied to the excitation coils 26. An AC waveform W indicates that an AC voltage is applied to the excitation coils 26 provided in the sensors 18 at positions corresponding to the AC waveform W. The lower diagram in Fig. 15 shows the positions of the sensors 18 at which the excitation coils 26 are provided.

[0027] 15 , the inventors considered switching the AC voltage applied to the plurality of excitation coils 26 at regular intervals so as to apply the AC voltage to the plurality of excitation coils 26 one by one in sequence. The inventors then considered that if a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated in the excitation coil 26 when the AC voltage is applied to the excitation coil 26 could be detected by a detection coil 28 provided in the same sensor 18, then the position of the plate edge of the steel sheet 14 could be detected from the relationship between the signal detected by the detection coil 28 and the position of the sensor 18, as described above.

[0028] However, it has been found that, for example, when multiple sensors 18 are arranged close to each other in the width direction of the device in order to increase the resolution when detecting the position of the plate end of the steel plate 14, simply switching the AC voltage applied to the multiple excitation coils 26 at regular intervals can cause the following problems.

[0029] 16 shows an example of the flow of magnetic flux when voltage is applied to multiple excitation coils 26 using a voltage application method according to a reference example. Fig. 16 shows the timing when an AC voltage is applied to one excitation coil 26A of the multiple excitation coils 26. At this timing, no AC voltage is applied to the excitation coils 26B and 26C located on either side of the one excitation coil 26A. In this case, the magnetic permeability of the yokes 24B and 24C, on which the excitation coils 26B and 26C are provided, is high, and magnetic flux M1 emitted from the north pole of the yoke 24A, on which the excitation coil 26A is provided, is absorbed by the south poles of the yokes 24B and 24C.

[0030] Furthermore, the south pole of yoke 24A absorbs magnetic flux M2 that passes through the interior of yokes 24B and 24C and is emitted from the north poles of yokes 24B and 24C. As a result, the magnetic flux path M from the north pole of yoke 24A to the south pole of yoke 24A disappears. Therefore, it was found that simply switching the AC voltage applied to the multiple excitation coils 26 at regular intervals does not provide the magnetic flux path M, and therefore there is a problem in that when an AC voltage is applied to excitation coil 26, a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of steel plate 14 on the magnetic field generated in excitation coil 26 cannot be detected by detection coil 28 provided in the same sensor 18.

[0031] Here, the inventors believed that this was caused by high magnetic permeability of the yokes 24 on both sides of the yoke 24 provided with the excitation coil 26 that generated the magnetic field, and thought that it would be sufficient to lower the magnetic permeability of the adjacent yokes 24. The inventors then thought that since the magnetic characteristics of the ferrite core used in the yoke 24 are nonlinear and that the relative magnetic permeability (the ratio of the magnetic permeability of an object to the magnetic permeability of a vacuum) approaches 1 when a magnetic field of a certain strength or higher is applied, in order to lower the magnetic permeability of the adjacent yokes 24, it would be sufficient to apply a DC voltage to the excitation coils 26 of the adjacent yokes 24 when an AC voltage is applied to the excitation coil 26. A voltage application method according to a first embodiment devised by the inventors will now be described.

[0032] Fig. 5 shows an example of a method for applying voltage to the multiple excitation coils 26 according to the first embodiment. The upper diagram in Fig. 5 shows the relationship between the time when a voltage is applied to each excitation coil 26 and the position of the sensor 18. The AC waveform W indicates that an AC voltage is applied to the excitation coil 26 provided in the sensor 18 at the position corresponding to the AC waveform W, and "D" indicates that a DC voltage is applied to the excitation coil 26 provided in the sensor 18 at the position corresponding to "D". The lower diagram in Fig. 5 shows the position of the sensor 18 at which each excitation coil 26 is provided.

[0033] As shown in Figure 5, the inventors have devised a method of applying an AC voltage to a plurality of excitation coils 26 one by one in sequence, while applying a DC voltage to excitation coils 26 located on both sides of the excitation coil 26 to which the AC voltage is applied. With this method, when an AC voltage is applied to the excitation coil 26, a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated in the excitation coil 26 can be detected by a detection coil 28 provided in the same sensor 18. This will be explained in detail below.

[0034] 6 shows an example of the flow of magnetic flux when voltages are applied to multiple excitation coils 26 using the voltage application method according to the first embodiment. Fig. 6 illustrates the timing when an AC voltage is applied to one excitation coil 26A among the multiple excitation coils 26, and a DC voltage is applied to excitation coils 26B and 26C located on both sides of the excitation coil 26A. When a DC voltage is applied to excitation coils 26B and 26C, the magnetic permeability of the yokes 24B and 24C on which the excitation coils 26B and 26C are provided decreases. Therefore, a magnetic circuit is no longer formed between the yoke 24A and the yokes 24B and 24C, and a magnetic flux path M is formed from the north pole of the yoke 24A to the south pole of the yoke 24A. Therefore, the magnetic flux emitted from the north pole of the yoke 24A is directed toward the south pole of the yoke 24A without being absorbed by the yokes 24B and 24C. This allows the detection coil 28 provided at the south pole of the yoke 24A to detect a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel plate 14 on the magnetic field generated in the excitation coil 26 of the yoke 24A.

[0035] Note that, although an example has been described in which a DC voltage is applied to the excitation coils 26B and 26C located one position away from one excitation coil 26A, a DC voltage may also be applied to the excitation coils 26 of one or more yokes 24 located near a yoke 24 to which an excitation coil 26 to which an AC voltage is applied is provided. The one or more yokes 24 located in a nearby position are selected based on the range of magnetic flux leakage from the yoke 24 to which an excitation coil 26 to which an AC voltage is applied is provided when a DC voltage is not applied to the excitation coils 26 of the one or more yokes 24 located in a nearby position. In other words, one or more yokes 24 located in a range where magnetic flux leaks from the yoke 24 are selected as the one or more yokes 24 located in a nearby position. In other words, the position near a yoke 24 to which an excitation coil 26 to which an AC voltage is applied is provided refers to the range of magnetic flux leakage from a yoke 24 to which an excitation coil 26 to which an AC voltage is applied is provided (specifically, the range affected by the magnetic flux emitted from the yoke 24). The range of magnetic flux leakage from the yoke 24 provided with the excitation coil 26 to which an AC voltage is applied can be determined by experiment or analysis.

[0036] Furthermore, the one or more yokes 24 located in the proximity are selected as follows depending on the position of the sensor 18 provided with the excitation coil 26 to which an AC voltage is applied. For example, in the case of a yoke 24 located between the yokes 24 at both ends of the multiple yokes 24 aligned in the device width direction, a yoke 24 exists adjacent to both of the yokes 24 to which the excitation coil 26 to which an AC voltage is applied is provided, so the one or more yokes 24 located adjacent to one of the yokes 24 to which the excitation coil 26 to which an AC voltage is applied is provided and the one or more yokes 24 located adjacent to the other yoke are selected as the one or more yokes 24 located in the proximity. Furthermore, in the case of an end yoke 24 among the multiple yokes 24 aligned in the device width direction, a yoke 24 exists adjacent to only one of the yokes 24 to which the excitation coil 26 to which an AC voltage is applied is provided, so the one or more yokes 24 located adjacent to one of the yokes 24 to which the excitation coil 26 to which an AC voltage is applied is selected as the one or more yokes 24 located in the proximity.

[0037] In this way, when a DC voltage is applied to the excitation coil 26 of one or more yokes 24 present in the range where magnetic flux leaks from the excitation coil 26A, it is possible to prevent the magnetic flux emitted from the north pole of the yoke 24A to which the excitation coil 26A is attached from being absorbed by one or more yokes 24 present in the range where the magnetic flux leaks. This allows the detection coil 28 provided on the south pole of the same yoke 24A to detect a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated in the excitation coil 26 of the yoke 24A. In this way, according to the voltage application method of the first embodiment, it is possible to detect a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated in the excitation coil 26 by the detection coil 28 provided on the same sensor 18.

[0038] Next, a specific configuration of the processing device 20 according to the first embodiment will be described. Fig. 7 shows an example of the configuration of the processing device 20. The processing device 20 is a device that performs various controls and various calculations related to the strip edge detection device 10, and is configured by a computer. The processing device 20 has a processor 42, a volatile memory 44, a non-volatile memory 46, an output circuit 48, and an input circuit 50. The processor 42, the volatile memory 44, the non-volatile memory 46, the input circuit 50, and the output circuit 48 are connected to each other so as to be able to communicate with each other via a bus 52 or the like.

[0039] The processor 42 includes, for example, a central processing unit (CPU) or a microprocessor unit (MPU). The volatile memory 44 includes, for example, random access memory (RAM) and temporarily stores programs and data as a working area. The non-volatile memory 46 includes, for example, read only memory (ROM), a hard disk drive (HDD), or a solid state drive (SSD), and stores various programs including an operating system and various data.

[0040] The non-volatile memory 46 stores a program for executing a process for detecting the position of the plate edge of the steel plate 14 (hereinafter referred to as "plate edge detection process"). The processor 42 reads the program from the non-volatile memory 46 and executes the program using the volatile memory 44 as a work area. The processor 42 controls the output circuit 48 and performs arithmetic processing based on signals input from the input circuit 50 in accordance with the program stored in the non-volatile memory 46.

[0041] The processing device 20 may have an electronic circuit such as a programmable logic device (PLD) or an application specific integrated circuit (ASIC) instead of or in addition to the processor 42. Some or all of the functions of the processor 42 may be realized by the electronic circuit such as the PLD or ASIC.

[0042] The excitation coil 26 of each sensor 18 is electrically connected to the output circuit 48. The output circuit 48 is controlled by the processor 42 to apply a voltage to each excitation coil 26. The detection coil 28 of each sensor 18 is electrically connected to the input circuit 50. When a signal output from the detection coil 28 is input to the input circuit 50, the input circuit 50 A / D converts the analog signal output from the detection coil 28 into a digital signal and outputs the digitized signal to the processor 42.

[0043] The processor 42 reads out a program for executing the strip edge detection process from the non-volatile memory 46, and deploys and executes the read program in the volatile memory 44, thereby functioning as each functional unit of the processing device 20. Specifically, the processor 42 functions as a voltage control unit 62 and an arithmetic processing unit 66.

[0044] The voltage control unit 62 is a functional unit that controls the output circuit 48 to apply voltage to the excitation coils 26 of the multiple yokes 24. The voltage control unit 62 selects one yoke 24 from the multiple yokes 24 by switching between them in order at regular time intervals, and controls the application of AC voltage to the excitation coil 26 of the selected yoke 24.

[0045] Furthermore, when an AC voltage is applied to the excitation coil 26, the voltage control unit 62 controls the voltage to be applied to the excitation coil 26 of the yoke 24 located in the above-mentioned close position so as to prevent magnetic flux from leaking from the yoke 24 to which the excitation coil 26 to which the AC voltage is applied is provided to the yoke 24 located in the vicinity of the yoke 24 to which the excitation coil 26 to which the AC voltage is applied is provided.

[0046] Specifically, when an AC voltage is applied to the excitation coil 26 of a selected yoke 24, the voltage control unit 62 selects a predetermined number of yokes 24 that are adjacent to the selected yoke 24 from the multiple yokes 24 as the yokes 24 located in the close position, and performs control to apply a DC voltage to the excitation coils 26 of the selected yokes 24. For example, while applying an AC voltage to the excitation coils 26, the voltage control unit 62 controls the output circuit 48 to apply a DC voltage to the excitation coils 26 of the nearby yokes 24. This suppresses leakage of magnetic flux from the yoke 24 to which the excitation coil 26 to which the AC voltage is applied is provided to the yoke 24 located in the close position to the yoke 24 to which the AC voltage is applied. Therefore, when an AC voltage is applied to the excitation coil 26, a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel plate 14 on the magnetic field generated in the excitation coil 26 is detected by the detection coil 28 provided in the same sensor 18.

[0047] The voltage control unit 62 may perform the following control as an example of controlling the application of a DC voltage to the excitation coil 26 of a yoke 24 that is located within a range of magnetic flux leakage from the yoke 24 to which the excitation coil 26 to which the AC voltage is applied is provided when an AC voltage is applied to the excitation coil 26 of the selected yoke 24. That is, when the selected yoke 24 is located at an end, the voltage control unit 62 may perform control to apply a DC voltage to the excitation coils 26 of at least a predetermined number (plurality) of yokes 24 that are located adjacent to one side of the selected yoke 24, among the multiple yokes 24. Furthermore, when the selected yoke 24 is located other than at an end, the voltage control unit 62 may perform control to apply a DC voltage to the excitation coils 26 of at least a predetermined number (plurality) of yokes 24 that are located on both sides of the selected yoke 24, among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at an end, the voltage control unit 62 may perform control to apply a DC voltage to the excitation coil 26 of at least one yoke 24 that is adjacent to one of the selected yokes 24 among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at a position other than the end, the voltage control unit 62 may perform control to apply a DC voltage to the excitation coil 26 of at least one yoke 24 that is adjacent to both sides of the selected yoke 24 among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at an end, the voltage control unit 62 may perform control to apply a DC voltage to the excitation coil 26 of one yoke 24 that is adjacent to one of the selected yokes 24 among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at a position other than the end, the voltage control unit 62 may perform control to apply a DC voltage to the excitation coil 26 of one yoke 24 that is adjacent to one of the selected yokes 24 among the multiple yokes 24.

[0048] The arithmetic processing unit 66 detects the position of the plate end of the steel sheet 14 from the relationship between the amount of change in the signals detected by all of the detection coils 28 and the positions of the sensors 18. Specifically, the arithmetic processing unit 66 acquires the signals detected by the detection coils 28 for each position of the sensors 18 in accordance with the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated by the excitation coil 26. For example, the input circuit 50 is provided with multiple channels to which signals from the detection coils 28 are input. Each channel is assigned a position of each sensor 18. When acquiring a signal from each channel, the arithmetic processing unit 66 identifies the position of the sensor 18 corresponding to each signal based on the identification information of each channel. Then, the arithmetic processing unit 66 detects the position of the plate end of the steel sheet 14 from the relationship between the amount of change in the signals acquired for each position of the sensors 18 and the positions of the sensors 18.

[0049] 8 shows an example of the flow of the edge detection process executed by the processor 42 of the processing device 20. The edge detection method by the edge detection device 10 is executed by the processor 42 executing the edge detection process.

[0050] First, in step S10, the voltage control unit 62 controls the voltage applied to the excitation coils 26 of the multiple yokes 24. Specifically, the voltage control unit 62 selects a yoke 24 from the multiple yokes 24, and performs control to apply an AC voltage to the excitation coil 26 of the selected yoke 24. Furthermore, when the voltage control unit 62 applies an AC voltage to the excitation coil 26 of the selected yoke 24, it selects a predetermined number of yokes 24 that are adjacent to the selected yoke 24 from the multiple yokes 24, and performs control to apply a DC voltage to the excitation coils 26 of the selected yokes 24. Step S10 is an example of a voltage control step of the present disclosure.

[0051] Next, in step S12, when an AC voltage is applied to the excitation coil 26 of the corresponding yoke 24, the detection coil 28 detects a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel plate 14 on the magnetic field generated in the excitation coil 26. Step S12 is an example of a detection step in the present disclosure.

[0052] Next, in step S14, the calculation processing unit 66 detects the position of the plate edge of the steel plate 14 from the relationship between the amount of change in the signal detected by the detection coil 28 and the position of the sensor 18. After step S14, the plate edge detection process ends.

[0053] As described above, in the strip edge detection device 10 according to the first embodiment, the voltage control unit 62 selects one yoke 24 from the plurality of yokes 24 by sequentially switching between them at regular time intervals, and controls the application of an AC voltage to the excitation coil 26 of the selected yoke 24. Furthermore, when the AC voltage is applied to the excitation coil 26 of the selected yoke 24, the voltage control unit 62 controls the application of a DC voltage to the excitation coils 26 of a predetermined number of yokes 24 that are adjacent to the selected yoke 24. This prevents magnetic flux from leaking from the yoke 24 to which the excitation coil 26 to which the AC voltage is applied is provided to a yoke 24 located close to the yoke 24 to which the AC voltage is applied. This allows the detection coil 28 provided in the same sensor 18 to detect a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated in the excitation coil 26 when the AC voltage is applied to the excitation coil 26.

[0054] Furthermore, by detecting a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated in the excitation coil 26 with the detection coil 28 provided in the same sensor 18, the signal detected by the detection coil 28 can be acquired for each position of the sensor 18. Then, the calculation processing unit 66 detects the position of the plate end of the steel sheet 14 from the relationship between the amount of change in the acquired signal and the position of the sensor 18.

[0055] Furthermore, the sheet edge detection device 10 according to the first embodiment detects the position of the sheet edge of the steel sheet 14 using a magnetic field that is not affected by water vapor, large amounts of water, etc. Therefore, when detecting the position of the sheet edge of the steel sheet 14, it is possible to avoid being affected by water vapor, large amounts of water, etc.

[0056] Furthermore, since the multiple detection coils 28 are arranged in a row in the width direction of the device, the position of the end of the steel plate 14 can be detected even if the position of the end of the steel plate 14 fluctuates significantly in the width direction of the device.

[0057] In the first embodiment, when an AC voltage is applied to the excitation coil 26, the voltage control unit 62 performs control to apply a DC voltage to the excitation coil 26 of the yoke 24 that is located in a nearby position. However, when an AC voltage is applied to the excitation coil 26, the voltage control unit 62 may perform control to apply a DC voltage to the excitation coil 26 of the yoke 24 that is located in a position other than the nearby position, or may perform control to apply a DC voltage to all of the remaining excitation coils 26.

[0058] Second Embodiment Next, a second embodiment of the present disclosure will be described.

[0059] In the second embodiment, the method of applying voltage to the plurality of excitation coils 26 is changed from that in the first embodiment. Fig. 9 shows an example of the method of applying voltage to the plurality of excitation coils 26 according to the second embodiment. As in Fig. 5 , the upper diagram in Fig. 9 shows the relationship between the time when a voltage is applied to each excitation coil 26 and the position of the sensor 18. The AC waveform W indicates that an AC voltage is applied to the excitation coil 26 provided in the sensor 18 at a position corresponding to the AC waveform W. The lower diagram in Fig. 9 shows the position of the sensor 18 at which each excitation coil 26 is provided.

[0060] The voltage control unit 62 (see FIG. 6 ) selects one yoke 24 from the plurality of yokes 24 by sequentially switching between them at regular time intervals, and performs control to apply an AC voltage to the excitation coil 26 of the selected yoke 24. Furthermore, when applying an AC voltage to the excitation coil 26 of the selected yoke 24, the voltage control unit 62 selects a predetermined number of yokes 24 from the plurality of yokes 24 that are adjacent to the selected yoke 24 as nearby yokes 24, and performs control to apply an AC voltage to the excitation coil 26 of the selected yoke 24. For example, while applying an AC voltage to the excitation coil 26, the voltage control unit 62 controls the output circuit 48 to apply an AC voltage having the same frequency and phase as the AC voltage applied to the excitation coil 26 to the excitation coil 26 of the nearby yoke 24. The nearby yoke 24 can be selected in the same manner as in the first embodiment.

[0061] The voltage control unit 62 may perform the following control as an example of controlling the application of an AC voltage to the excitation coils 26 of the yokes 24 that are located within a range of magnetic flux leakage from the yoke 24 to which the excitation coil 26 to which the AC voltage is applied is provided when the AC voltage is applied to the excitation coil 26 of the selected yoke 24. That is, when the selected yoke 24 is located at an end, the voltage control unit 62 may perform control to apply an AC voltage to the excitation coils 26 of at least a predetermined number (plurality) of yokes 24 that are located adjacent to one side of the selected yoke 24, among the multiple yokes 24. Furthermore, when the selected yoke 24 is located other than at an end, the voltage control unit 62 may perform control to apply an AC voltage to the excitation coils 26 of at least a predetermined number (plurality) of yokes 24 that are located on both sides of the selected yoke 24, among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at an end, the voltage control unit 62 may perform control to apply an AC voltage to the excitation coil 26 of at least one yoke 24 that is adjacent to one of the selected yokes 24 among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at a position other than the end, the voltage control unit 62 may perform control to apply an AC voltage to the excitation coil 26 of at least one yoke 24 that is adjacent to both sides of the selected yoke 24 among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at an end, the voltage control unit 62 may perform control to apply an AC voltage to the excitation coil 26 of one yoke 24 that is adjacent to one of the selected yokes 24 among the multiple yokes 24. Furthermore, when the selected yoke 24 is located at a position other than the end, the voltage control unit 62 may perform control to apply an AC voltage to the excitation coil 26 of one yoke 24 that is adjacent to one of the selected yokes 24 among the multiple yokes 24.

[0062] As in the second embodiment, when an AC voltage is applied to the excitation coil 26 of a nearby yoke 24, the magnetic flux emitted from one yoke 24 does not intersect with the magnetic flux emitted from another yoke 24, and therefore, it is possible to prevent a magnetic circuit from being formed between the yoke 24A and the yokes 24B and 24C, as described in Fig. 16. This makes it possible to form a magnetic flux path M within the same sensor 18, and therefore, when an AC voltage is applied to the excitation coil 26, a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel plate 14 on the magnetic field generated in the excitation coil 26 can be detected by the detection coil 28 provided in the same sensor 18.

[0063] In the second embodiment, when an AC voltage is applied to the excitation coil 26, the voltage control unit 62 controls the application of the AC voltage to the excitation coil 26 of the yoke 24 that is located in a nearby position. However, when an AC voltage is applied to the excitation coil 26, the voltage control unit 62 may also control the application of the AC voltage to the excitation coil 26 of the yoke 24 that is located in a position other than the nearby position.

[0064] Third Embodiment Next, a third embodiment of the present disclosure will be described.

[0065] In the third embodiment, the method of applying voltage to the plurality of excitation coils 26 is changed from that in the first embodiment. Fig. 10 shows an example of the method of applying voltage to the plurality of excitation coils 26 according to the third embodiment. As in Fig. 5 , the upper diagram in Fig. 10 shows the relationship between the time when a voltage is applied to each excitation coil 26 and the position of the sensor 18. The AC waveform W indicates that an AC voltage is applied to the excitation coil 26 provided in the sensor 18 at a position corresponding to the AC waveform W. The lower diagram in Fig. 10 shows the position of the sensor 18 at which each excitation coil 26 is provided.

[0066] The voltage control unit 62 (see FIG. 6) performs control to apply AC voltage to all of the excitation coils 26 of the plurality of yokes 24 without switching the application of AC voltage to the excitation coils 26 of the plurality of yokes 24 .

[0067] As in the third embodiment, even if an AC voltage is applied to all of the excitation coils 26 of the plurality of yokes 24 without switching the application of the AC voltage to the excitation coils 26 of the plurality of yokes 24, the magnetic flux emitted from one yoke 24 does not intersect with the magnetic flux emitted from another yoke 24, and therefore, it is possible to prevent the formation of a magnetic circuit M between the yoke 24A and the yokes 24B and 24C, as described in Fig. 15. This makes it possible to form a magnetic flux path M within the same sensor 18, and therefore, when an AC voltage is applied to the excitation coil 26, a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel plate 14 on the magnetic field generated in the excitation coil 26 can be detected by the detection coil 28 provided in the same sensor 18.

[0068] Fourth Embodiment Next, a fourth embodiment of the present disclosure will be described.

[0069] 11 and 12 show an example of a sensor 118 according to the fourth embodiment. In the fourth embodiment, a single sensor 118 is used instead of the multiple sensors 18 of the first embodiment. The sensor 118 includes a yoke 124, an excitation coil 126, and multiple detection coils 128. The yoke 124 is made of a magnetic material such as a ferrite core, and includes a pair of core portions 132 and a connecting portion 134. The pair of core portions 132 extend vertically, and the connecting portion 134 connects the lower ends of the pair of core portions 132 together. The yoke 124 is provided to extend in the conveyance direction.

[0070] The excitation coil 126 is wound around one of a pair of core portions 132 via a bobbin (not shown). The excitation coil 126 is wound around one of the core portions 132 and extends in the conveyance direction. The multiple detection coils 128 are arranged side by side in the device width direction. Each detection coil 128 is arranged above the other core portion 132 of the pair of core portions 132. The sensor 118 has one excitation coil 126 for the multiple detection coils 128, and the excitation coil 126 is used in common for the multiple detection coils 128.

[0071] 13 shows an example of the configuration of a processing device 20 according to the fourth embodiment. The processing device 20 differs from the first embodiment in that the processor 42 functions as a voltage control unit 62 and an arithmetic processing unit 66. The voltage control unit 62 controls the output circuit 48 to apply an AC voltage to an excitation coil 126 of a yoke 124 extending in the width direction of the device.

[0072] The arithmetic processing unit 66 detects the position of the plate end of the steel sheet 14 from the relationship between the amount of change in the signal detected by the detection coil 128 and the position of the sensor 118. Specifically, the arithmetic processing unit 66 acquires the signal detected by the detection coil 128 for each position of the detection coil 128 in accordance with the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated by the excitation coil 126. For example, the input circuit 50 is provided with multiple channels to which signals from each detection coil 128 are input. Each channel is assigned a position of each detection coil 128. When acquiring a signal from each channel, the arithmetic processing unit 66 identifies the position of the detection coil 128 corresponding to each signal based on the identification information of each channel. Then, the arithmetic processing unit 66 detects the position of the plate end of the steel sheet 14 from the relationship between the amount of change in the signal acquired for each position of the detection coil 128 and the position of the detection coil 128.

[0073] 14 shows an example of the flow of the edge detection process executed by the processor 42 of the processing device 20. The edge detection method by the edge detection device 10 is executed by the processor 42 executing the edge detection process.

[0074] First, in step S20, the voltage control unit 62 controls the output circuit 48 to apply an AC voltage to the excitation coil 126 of the yoke 124 that extends in the device width direction. Step S20 is an example of a voltage control step of the present disclosure.

[0075] Next, in step S22, when an AC voltage is applied to the excitation coil 126, each detection coil 128 detects a signal corresponding to the strength of the magnetic field generated in the excitation coil 126. Step S22 is an example of a detection step in the present disclosure.

[0076] Next, in step S24, the calculation processing unit 66 detects the position of the plate edge of the steel plate 14 from the relationship between the amount of change in the signal detected by the detection coil 128 and the position of the detection coil 128. After step S24, the plate edge detection process ends. Step S24 is an example of a calculation processing step of the present disclosure.

[0077] As described above, in the strip edge detection device 10 according to the fourth embodiment, the voltage control unit 62 controls the application of an AC voltage to the excitation coil 126 provided on the yoke 124. Here, the yoke 124 and the excitation coil 126 are provided to extend in the width direction of the device. Therefore, magnetic flux emitted from the yoke 124 does not leak to another yoke. As a result, when an AC voltage is applied to the excitation coil 126, each detection coil 128 can detect a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel sheet 14 on the magnetic field generated in the excitation coil 126.

[0078] Furthermore, by detecting a signal corresponding to the strength of the magnetic field obtained by reflecting the influence of the steel plate 14 on the magnetic field generated in the excitation coil 126 with each detection coil 128, the amount of change in the magnetic field strength can be obtained for each position of the detection coil 128. Then, the calculation processing unit 66 detects the position of the plate end of the steel plate 14 from the relationship between the amount of change in the magnetic field strength and the position of the detection coil 128.

[0079] Furthermore, the sheet edge detection device 10 according to the fourth embodiment detects the position of the sheet edge of the steel sheet 14 using a magnetic field that is not affected by water vapor, large amounts of water, etc. Therefore, when detecting the position of the sheet edge of the steel sheet 14, it is possible to avoid being affected by water vapor, large amounts of water, etc.

[0080] Furthermore, since the multiple detection coils 28 are arranged in a row in the width direction of the device, the position of the end of the steel plate 14 can be detected even if the position of the end of the steel plate 14 fluctuates significantly in the width direction of the device.

[0081] The above describes the first to fourth embodiments of the present disclosure, but the present disclosure is not limited to the above, and it goes without saying that various modifications can be made within the scope of the present disclosure without departing from its spirit.

[0082] The disclosure of Japanese Application No. 2024-035344, filed on March 7, 2024, is incorporated herein by reference in its entirety.

[0083] REFERENCE SIGNS LIST 10 Sheet edge detection device 12 Conveyor roll 14 Steel sheet 16 Cooling device 18 Sensor 20 Processing device 24 Yoke 26 Excitation coil 28 Detection coil 118 Sensor 124 Yoke 126 Excitation coil 128 Detection coil

Claims

1. A plate edge detection device that detects the position of the plate edge of a steel plate being transported through a cooling device that cools the steel plate, comprising: a plurality of ferromagnetic core materials that are arranged in a line in the width direction of the plate edge detection device, corresponding to the plate width direction of the steel plate, and each having an excitation coil provided thereon; a plurality of detection coils that correspond to each of the plurality of ferromagnetic core materials and detect a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on the magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil of the corresponding ferromagnetic core material; a voltage control unit that controls the voltage applied to the excitation coils of the plurality of ferromagnetic core materials; and an arithmetic processing unit that detects the position of the plate edge of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil, wherein the voltage control unit controls the application of a voltage to the excitation coil of at least one ferromagnetic core material among the plurality of ferromagnetic core materials that is present within a range of magnetic flux leakage from the ferromagnetic core material provided with the excitation coil to which the AC voltage is applied.

2. The plate edge detection device described in claim 1, wherein the voltage control unit selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in sequence at regular time intervals, controls the application of an AC voltage to the excitation coil of the selected ferromagnetic core material, and controls the application of a DC voltage to the excitation coils of at least a predetermined number of ferromagnetic core materials that are adjacent to the selected ferromagnetic core material among the plurality of ferromagnetic core materials when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material.

3. The plate edge detection device described in claim 1, wherein the voltage control unit selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in sequence at regular time intervals, controls the application of an AC voltage to the excitation coil of the selected ferromagnetic core material, and controls the application of a DC voltage to the excitation coil of at least one ferromagnetic core material, among the plurality of ferromagnetic core materials, that is located next to the selected ferromagnetic core material, when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material.

4. The plate edge detection device described in claim 1, wherein the voltage control unit selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in sequence at regular time intervals, controls the application of an AC voltage to the excitation coil of the selected ferromagnetic core material, and when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material, controls the application of an AC voltage to the excitation coils of at least a predetermined number of ferromagnetic core materials that are adjacent to the selected ferromagnetic core material among the plurality of ferromagnetic core materials.

5. A plate edge detection device as described in claim 1, wherein the voltage control unit selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in sequence at regular time intervals, controls the application of an AC voltage to the excitation coil of the selected ferromagnetic core material, and when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material, controls the application of an AC voltage to the excitation coil of at least one ferromagnetic core material among the plurality of ferromagnetic core materials that is located next to the selected ferromagnetic core material.

6. A plate edge detection device according to claim 1, wherein the voltage control unit controls the application of AC voltage to all of the excitation coils of the plurality of ferromagnetic core materials.

7. A plate edge detection device that detects the position of the plate edge of a steel plate being transported through a cooling device that cools the steel plate, comprising: a ferromagnetic core material provided with an excitation coil; a plurality of detection coils that are arranged in a row in the width direction of the plate edge detection device corresponding to the plate width direction of the steel plate, and that detect a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on the magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil; a voltage control unit that controls the application of voltage to the excitation coil; and an arithmetic processing unit that detects the position of the plate edge of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil, wherein the ferromagnetic core material and the excitation coil are provided extending in the width direction, and the voltage control unit controls the application of AC voltage to the excitation coil of the ferromagnetic core material provided extending in the width direction.

8. A plate edge detection method for detecting the position of the plate edge of a steel plate being transported in a cooling device that cools the steel plate, comprising: a plate edge detection device having: a plurality of ferromagnetic core materials arranged side by side in the width direction of the plate edge detection device corresponding to the plate width direction of the steel plate, each provided with an excitation coil; a plurality of detection coils corresponding to each of the plurality of ferromagnetic core materials, and detecting a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on a magnetic field generated in the excitation coil of the corresponding ferromagnetic core material when an AC voltage is applied to the excitation coil; a voltage control unit controlling the voltage applied to the excitation coils of the plurality of ferromagnetic core materials; and an arithmetic processing unit detecting the position of the plate edge of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil; a detection step of using the plurality of detection coils to detect a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on the magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil of the corresponding ferromagnetic core material, using the plurality of detection coils; and a calculation processing step of using the calculation processing unit to detect the position of the plate end of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil, wherein the voltage control step controls the application of a voltage to the excitation coil of at least one ferromagnetic core material among the plurality of ferromagnetic core materials that is present in a range where magnetic flux leaks from the ferromagnetic core material to which the excitation coil to which the AC voltage is applied is provided.

9. A plate end detection method as described in claim 8, wherein the voltage control step selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in order at regular time intervals, performs control to apply an AC voltage to the excitation coil of the selected ferromagnetic core material, and performs control to apply a DC voltage to the excitation coil of at least a predetermined number of ferromagnetic core materials that are adjacent to the selected ferromagnetic core material among the plurality of ferromagnetic core materials when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material.

10. A plate end detection method as described in claim 8, wherein the voltage control step selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in order at regular time intervals, controls the application of an AC voltage to the excitation coil of the selected ferromagnetic core material, and controls the application of a DC voltage to the excitation coil of at least one ferromagnetic core material, among the plurality of ferromagnetic core materials, that is located next to the selected ferromagnetic core material, when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material.

11. A plate end detection method as described in claim 8, wherein the voltage control step selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in order at regular time intervals, performs control to apply an AC voltage to the excitation coil of the selected ferromagnetic core material, and performs control to apply an AC voltage to the excitation coil of at least a predetermined number of ferromagnetic core materials that are adjacent to the selected ferromagnetic core material among the plurality of ferromagnetic core materials when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material.

12. A plate end detection method as described in claim 8, wherein the voltage control step selects a ferromagnetic core material from the plurality of ferromagnetic core materials by switching between them in order at regular time intervals, controls the application of an AC voltage to the excitation coil of the selected ferromagnetic core material, and controls the application of an AC voltage to the excitation coil of at least one ferromagnetic core material, among the plurality of ferromagnetic core materials, that is located next to the selected ferromagnetic core material when the AC voltage is applied to the excitation coil of the selected ferromagnetic core material.

13. The plate end detection method according to claim 8, wherein said voltage control step performs control to apply an AC voltage to all of the excitation coils of said plurality of ferromagnetic core materials.

14. A plate edge detection method for detecting the position of the plate edge of a steel plate being transported in a cooling device that cools the steel plate, comprising: a plate edge detection device having a ferromagnetic core member extending in the width direction of the plate edge detection device corresponding to the width direction of the steel plate and provided with an excitation coil; a plurality of detection coils arranged side by side in the width direction and detecting a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel plate on a magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil; a voltage control unit that controls the application of voltage to the excitation coil; and a calculation processing unit that detects the position of the plate edge of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil; and a voltage control step that uses the voltage control unit to control the application of AC voltage to the excitation coil of the ferromagnetic core member extending in the width direction. a detection step of using the plurality of detection coils to detect a signal corresponding to the strength of a magnetic field obtained by reflecting the influence of the steel sheet on the magnetic field generated in the excitation coil when an AC voltage is applied to the excitation coil; and a calculation processing step of using the calculation processing unit to detect the position of the plate end of the steel plate from the relationship between the amount of change in the signal detected by the detection coil and the position of the detection coil when an AC voltage is applied to the excitation coil.

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